:Objective To study theprotective effects of penequinine hydrochloride on paraquat-induced acute lung injury inrats. Methods Fifty-four male SD rats were all injected intraperitoneally with paraquat(25 mg/kg) to induce lung injury (PQ groups), or with the same volume of normal saline(control group). Penequinine hydrochloride (0.3 mg/kg) was injected intraperitoneally 2 hlater in half amount rats of the study group, and the same volume of normal saline wasinjected in another half amunfs (PHC group). Rats were sacrificed 6, 24, 48 or 72 h afterpenequinine hydrochloride or saline injection. The malondialdehyde (MDA) level andsuperoxide dismutade (SOD) activity in both plasma and bronchoalveolar lavage fluid (BALF)were detected, respectively. Expression of nuclear factor kappa B (NF-κB)p65 in lung was measured with immunohistochemistry staining, and lung wet/dry weight ratio(W/D) was calculated. Results MDA level in PQ group increased significantly both in plasmaand BALF (P<0.01), SOD activity decreased both in plasma and BALF (P<0.05)but increased significantly in BALF 48h later (P<0.01). After injection ofpenequinine hydrochloride, MDA decreased and SOD activity increased significantly in bothplasma and BALF (P<0.05). The pathological changes in lung tissue werelessened, and the expression of NF-κB p65 in lungs and W/D weredecreased after penequinine hydrochloride injected (P<0.05). Conclusion Penequinine hydrochloride has protectiveeffects on paraquat-induced acute lung injury in rats. Key words: Penequinine hydrochloride; Paraquat; Acute lung injury